Editing Beaufort scale (section)

==History==
[[File:FrancisBeaufort.jpg|thumb|[[Francis Beaufort|Sir Francis Beaufort]]]]
The scale that carries Beaufort's name had a long and complex evolution from the previous work of others (including [[Daniel Defoe]] the century before).  In the 18th century, naval officers made regular weather observations, but there was no standard scale and so they could be very subjective&nbsp;— one man's "stiff breeze" might be another's "soft breeze"—: Beaufort succeeded in standardising a scale.<ref name="Saucier-1955">{{Cite book|first=Walter Joseph |last=Saucier |year=1955 |title=Principles of Meteorological Analysis |location=Chicago |publisher=The University of Chicago Press |oclc=1082907714 }}, [https://books.google.com/books?id=CM99-uKpR00C reprinted in 2003 by Dover Publications.]</ref> The scale was devised in 1805 by [[Francis Beaufort]] (later [[Rear admiral (Royal Navy)|Rear Admiral]]), a [[Hydrography|hydrographer]] and a [[Royal Navy]] officer, while serving on {{ship|HMS|Woolwich|1785|6}}, and refined until he was [[Hydrographer of the Navy]] in the 1830s, when it was adopted officially.  It was first used during the 1831-1836 [[Second voyage of HMS Beagle|"Darwin voyage"]] of [[HMS Beagle|HMS ''Beagle'']] under Captain [[Robert FitzRoy]], who was later to set up the first [[Met Office|Meteorological Office]] in Britain giving regular weather forecasts.<ref name="met office">{{cite web|url=http://www.metoffice.gov.uk/media/pdf/4/4/Fact_Sheet_No._6_-_Beaufort_Scale.pdf|publisher=[[Met Office]]|title=National Meteorological Library and Archive Fact sheet 6 – The Beaufort Scale|access-date=2011-05-13|url-status=dead|archive-url=https://web.archive.org/web/20121002134429/http://www.metoffice.gov.uk/media/pdf/4/4/Fact_Sheet_No._6_-_Beaufort_Scale.pdf|archive-date=2 October 2012}}</ref>

The initial scale of 13 classes (zero to 12) did not reference [[wind speed]] numbers, but related qualitative wind conditions to effects on the sails of a [[Frigate#Heavy frigate|frigate]], then the main ship of the [[Royal Navy]], from "just sufficient to give steerage" to "that which no canvas sails could withstand".<ref>{{cite book |last = Oliver |first = John E. |title = Encyclopedia of world climatology |publisher = Springer |year = 2005}}</ref>

The scale was made a standard for ship's log entries on Royal Navy vessels in the late 1830s and, in 1853, the Beaufort scale was accepted as generally applicable at the [[International Meteorological Organization#History|First International Meteorological Conference in Brussels]].<ref name="Saucier-1955"/>

In 1916, to accommodate the growth of steam power, the descriptions were changed to how the sea, not the sails, behaved and extended to land observations. [[Anemometer]] rotations to scale numbers were standardised only in 1923. [[George Simpson (meteorologist)|George Simpson]], [[Order of the British Empire|CBE]] (later Sir George Simpson), director of the [[United Kingdom|UK]] Meteorological Office, was responsible for this and for the addition of the land-based descriptors.<ref name="met office"/> The measures were slightly altered some decades later to improve its utility for [[meteorologist]]s. Nowadays, meteorologists typically express wind speed in kilometres or miles per hour or, for maritime and aviation purposes, [[knot (unit)|knots]], but Beaufort scale terminology is still sometimes used in weather forecasts for shipping<ref>{{Cite book|last=McIlveen |first=Robin |year=1991 |title=Fundamentals of Weather and Climate |location=[[Cheltenham]], England |publisher=Stanley Thornes |page=[https://books.google.com/books?id=TmdlBqzl9WIC&pg=PA40 40] |isbn=978-0-7487-4079-6 }}</ref> and the [[severe weather]] warnings given to the public.<ref>{{Cite book|last=Hay |first=William W. |year=2016 |title=Experimenting on a Small Planet: A History of Scientific Discoveries, a Future of Climate Change and Global Warming |edition=second |location=Cham, Switzerland |publisher=Springer Verlag |page=[https://books.google.com/books?id=VpFPDAAAQBAJ&pg=PA26 26] |isbn=978-3-319-27402-7 }}</ref>

[[File:Beaufort wind scale.png|thumb|{{center|Data graphic showing Beaufort wind force in scale units, knots and metres/second}}]]
Wind speed on the Beaufort scale is based on the [[empirical relationship]]:<ref>{{Cite book|first=Tom |last=Beer |year=1997 |title =Environmental Oceanography |publisher=CRC Press |isbn=0-8493-8425-7 | url = https://books.google.com/books?id=pgZtaB-qOmYC&q=%22Beaufort+Scale%22+0.836&pg=PA224}}</ref>
* ''v'' = 0.836 ''B''<sup>3/2</sup> [[Metre per second|m/s]]
* ''v'' = 1.625 ''B''<sup>3/2</sup> [[Knot (unit)|knots]] (<math>=\frac{13} {8} \sqrt{B^3}</math>)

where ''v'' is the equivalent wind speed at 10 metres above the sea surface and ''B'' is Beaufort scale number. For example, ''B'' = 9.5 is related to 24.5&nbsp;m/s which is equal to the lower limit of "10 Beaufort". Using this formula the highest winds in hurricanes would be 23 in the scale. F1 [[tornado]]es on the [[Fujita scale]] and T2 [[TORRO scale]] also begin roughly at the end of level 12 of the Beaufort scale, but are independent scales, although the TORRO scale wind values are based on the 3/2 power law relating wind velocity to Beaufort force.<ref>{{cite web |last = Maiden |first = Terence |title = T-Scale: Origins and Scientific Basis |publisher = TORRO |url = http://www.torro.org.uk/TORRO/severeweather/Tscaleorigin.php |access-date = 2012-01-04 |url-status = dead |archive-url = https://web.archive.org/web/20120205020044/http://www.torro.org.uk/TORRO/severeweather/Tscaleorigin.php |archive-date = 5 February 2012}}</ref>

[[Wave height]]s in the scale are for conditions in the open ocean, not along the shore.